Support generic synchronization against an IPC::Channel

ipc/ipc_test.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 module IPC.mojom;
 
+import "mojo/common/event.mojom";
+
 interface SimpleTestDriver {
   ExpectValue(int32 value);
 
   [Sync]
   GetExpectedValue() => (int32 value);
 
   [Sync]
   RequestValue() => (int32 value);
 
   RequestQuit() => ();
 };
 
 interface SimpleTestClient {
   [Sync]
   RequestValue() => (int32 value);
 };
 
 interface PingReceiver {
   Ping() => ();
 };
 
 interface IndirectTestDriver {
   GetPingReceiver(associated PingReceiver& request);
 };
+
+interface SynchronizationTestClient {
+  OnTokenReceived(string token) => ();
+};
+
+interface SynchronizationTestSender {
+  SendToken(SynchronizationTestReceiver receiver,
+            SynchronizationTestClient client);
+  Quit();
+};
+
+interface SynchronizationTestReceiver {
+  ReceiveToken(string token,
+               SynchronizationTestClient client,
+               mojo.common.mojom.Event& event);
+};